[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] Modularizing QEMU RFC
From: |
Marc Marí |
Subject: |
Re: [Qemu-devel] Modularizing QEMU RFC |
Date: |
Mon, 3 Aug 2015 11:01:47 +0200 |
On Mon, 3 Aug 2015 16:22:34 +0800
Fam Zheng <address@hidden> wrote:
> On Mon, 08/03 09:52, Marc Marí wrote:
> > So any other ideas to reduce the library overhead are appreciated.
>
> It would be interesting to see your profiling on the library loading
> overhead. For example, how much does it help to reduce the library
> size, and how much does it help to reduce the # of libraries?
>
> The protocol drivers are modularized for the sake of library
> dependencies, so they should stay that way. However, we can
> "sensibly" combine all non-native format drivers (VMDK, VHDX, ...)
> into a cold-formats.so (if it turns out that loading one big .so is
> much faster than loading separate ones). But we should leave qcow2
> as a separate one for obvious reasons, or make a hot-formats.so with
> one or two other formats if that makes more sense.
>
> With that, for the first step, we can lazy load the cold-formats.so
> whenever we need to probe or a non-qcow2 format is involved. Then on
> top of that we can implement what Peter has suggested.
>
Some profiling:
A QEMU with this configuration:
./configure --enable-sparse --enable-sdl --enable-gtk --enable-vte \
--enable-curses --enable-vnc --enable-vnc-{jpeg,tls,sasl,png,ws} \
--enable-virtfs --enable-brlapi --enable-curl --enable-fdt \
--enable-bluez --enable-kvm --enable-rdma --enable-uuid --enable-vde \
--enable-linux-aio --enable-cap-ng --enable-attr --enable-vhost-net \
--enable-vhost-scsi --enable-spice --enable-rbd --enable-libiscsi \
--enable-smartcard-nss --enable-guest-agent --enable-libusb \
--enable-usb-redir --enable-lzo --enable-snappy --enable-bzip2 \
--enable-seccomp --enable-coroutine-pool --enable-glusterfs \
--enable-tpm --enable-libssh2 --enable-vhdx --enable-quorum \
--enable-numa --enable-tcmalloc --target-list=x86_64-softmmu
Has dependencies on 142 libraries. It takes 60 ms between the run and
the jump to the main function, and 80 ms between the run and the
first kvm_entry.
A QEMU with the same configuration and --enable-modules has
dependencies on 125 libraries. It takes 20 ms between the run and the
jump to the main function, and 100 ms between the run and the first
kvm_entry.
The libraries that are not loaded are: libiscsi, libcurl, librbd,
librados, ligfapi, libglusterfs, libgfrpc, libgfxdr, libssh2, libcrypt,
libidin, libgssapi, liblber, libldap, libboost_thread, libbost_system
and libatomic_ops.
As I already explained, the current implementation of modules loads
the modules at startup always. That's why the QEMU setup takes longer,
even though it uses G_MODULE_BIND_LAZY. And that's why I was proposing
hotplugging.
I don't know if loading one big library is more efficent than a lot of
small ones, but it would make sense.
Marc
Re: [Qemu-devel] Modularizing QEMU RFC, Daniel P. Berrange, 2015/08/03
Re: [Qemu-devel] Modularizing QEMU RFC, Paolo Bonzini, 2015/08/03